High altitude platforms e.g. situated from 300 m to less than 5 km and even higher, e.g. situated from 5 to 30 km altitude, have been proposed for a wide variety of applications. One area of growing interest is in providing from high altitude platforms information services such as telecommunications, positioning and observation capabilities including high speed internet, e-mail, telephony, televisual services, backhaul services, video-on-demand, global positioning, astronomical observations, atmospheric monitoring for example by LIDAR (light detection and ranging) and aerial photography.
Compared with satellites, high altitude platforms have several advantages, primarily because the distance from a transmitter to a receiver on Earth can be much less, with geostationary satellites typically at 36,000 km altitude and for a low Earth orbit satellite around 1000 km altitude.
This relative nearness of high altitude platforms can result in much stronger signals being received at Earth and near the Earth's surface, avoid the expense of rocket launches and can provide shorter development times.
U.S. Pat. No. 7,046,934 discloses a high altitude balloon for delivering information services in conjunction with a satellite.
However, there are numerous and significant technical challenges to providing reliable information service from a high altitude platform. A key problem is maintaining the stability of such a platform, which will be subject to winds which can be turbulent and of very high speeds. In particular, many information services require accurate directional transmissions which are difficult to deliver from a platform subject to the high winds present at such altitudes.
Furthermore the power available locally at altitude is generally restricted to a few kW, ruling out engineering solutions involving high powered devices.
Therefore, further improvements in these areas would be highly desirable.